Preparation And Electrochemical Properties Of Multifunctional Three-dimensional Transition Metal Phosphide Electrodes

Renewable clean energy such as water conservancy,tidal energy,wind energy,is quite inconvenient to store and collect in nature.Therefore,scientists have begun to pay more and more attention to new energy storage devices and energy conversion devices.Among energy devices,supercapacitors with high power density,high cycle times,fast charging and discharging time are considered to be one of the most promising alternatives to a new generation of high-performance power supplies.They have great application potential in the field of sustainable energy development.At the same time,to promote the sustainable development of human society in the future,hydrogen energy(H₂)as the best clean energy has also attracted more and more attention from various countries.Therefore,searching for a multifunctional non-noble metal electrode material that can be used for supercapacitor,hydrogen evolution and oxygen evolution reaction plays an important role in promoting the utilization and development of new energy.This paper uses carbon fiber cloth as a flexible conductive substrate,one-dimensional nickel-cobalt transition metal phosphide nanowires and two-dimensional nickel-cobalt double hydroxide nanosheets to construct three-dimensional electrodes.Their performance as supercapacitor electrodes and hydrogen and oxygen evolution electrodes have been tested.The main contents of electrochemical performance are as follows:Using carbon cloth as a conductive substrate,the three-dimensional self-supporting Ni Co P@Ni Co LDH/CC electrodes were prepared by hydrothermal,modified phosphating and electrodeposition methods.Firstly,one-dimensional(1D)alkaline nickel cobalt carbonate nanowires(NWs)are grown in situ by hydrothermal method;secondly,one-dimensional Ni Co P NWs are obtained by soaking in Na H₂PO₂solution and then calcining and phosphating;finally,two-dimensional(2D)Ni Co LDH nanosheets are loaded on Ni Co P NWs by electrodeposition to construct a three-dimensional(3D)Ni Co P@Ni Co LDH/CC electrode.(1)When used as a supercapacitor electrode,the area specific capacitance is 9.4F cm^-2 at 10 m A cm^-2 in 3 M KOH electrolyte,the capacitance retention rate is 74.12%at 50 m A cm^-2.The capacitance retention rate reached 93.51%after 5000 cycles.(2)As an electrocatalytic HER and OER electrode,when the hydrogen evolution reaction occurs in an alkaline electrolyte,the overpotential is as low as 178 m V at a current density of 10 m A cm^-2,the Tafel slope is 80 m V dec^-1.In an acidic electrolyte,the overpotential is 114 m V at a current density of 10 m A cm^-2,the Tafel slope is 79m V dec^-1.When used as an oxygen evolution electrode,it has an overpotential of 310m V at a current density of 10 m A cm^-2 in an alkaline electrolyte,the Tafel slope is 115m V dec^-1.The reason for the improvement of electrochemical performance is mainly due to the Ni Co P@Ni Co LDH nanostructure grown on the conductive carbon cloth substrate,and the three-dimensional structure constructed shows a good synergistic effect.This work provides a simple strategy for constructing multifunctional transition metal phosphide materials with three-dimensional hierarchical structure,and shows good application prospects in energy storage process and conversion.